docs: def get_amount_arrears_transactions(self, billing_cycle):
          """Get the sum of all transaction legs in to_account during given billing cycle"""
          previous_billing_cycle = billing_cycle.get_previous()
          if not previous_billing_cycle:
              return Decimal(0)
          return self.to_account.balance(
              transaction__date__lt=previous_billing_cycle.date_range.upper,
              transaction__date__gte=previous_billing_cycle.date_range.lower,
          )